There are three numbers a, B and C. The average number of a and B is 15, the average number of B and C is 19, and the average number of a and C is 17?

A+B=15*2=30①
B+C=19*2=38②
A+C=17*2=34③
Triple addition
2（A+B+C)=30+38+34=102
A+B+C=51④
④-①
C=21
④-③
B=17
④-②
A=13

It is known that a and B represent a and B on the number axis respectively (1) fill in the following table according to the number axis: a6-6-62-1.5b40-4-10-1.5a, distance 2 between two points of B__________________ 0 (2) if the distance between a and B is D, what is the quantitative relationship between D and a and B? (3) Mark all the qualified integer points P on the number axis so that the sum of the distances from it to 10 and - 10 is 20, and find the sum of all these integers. (4) find out the point P of (3) which satisfies that the difference between the distances to 10 and - 10 is greater than 1 but less than 5. (5) if the number represented by point C is x, where is the minimum value of | x + 1 | + | X-2 |?

(1) Fill in the table as follows: a6-6-62-1.5b40-4-10-1.5a, the distance between two points B 262120 (2) from (1) can be obtained: D = | A-B | or D = | B-A |; (3) as long as the integers between - 10 and 10 satisfy that the sum of the distances between - 10 and 10 is 20, there are: - 10, - 9, - 8, - 7, - 6, - 5, - 4, - 3, - 2, - 1, 0

If two points on the number axis are a and B, what is the distance between them?
How much is it? Please tell me the reason

Distance = B-A
If 2 and 5 are on the number axis, the distance between them is 5-2 = 3
Or 5 and 2 on the number axis, the distance between them is 2-5 = 3

There is a column of numbers - 12, 25, - 310417 Then the seventh number is______ ．

If the numerator of the seventh number is 7 and the denominator is 72 + 1 = 50, then the seventh number is - 750

There is a sequence of numbers: 1,5,9,13,17 What's the 56th number?

The 56th number is 221
The first number is 1, the second number is 5, which is (1 + 4), the third number is (1 + 2 * 4), and the 56th number is (1 + 55 * 4)

1.5.9.13.17.21 what is the 1000th item in this column? What is 4921

The general term is an = an-1 + 4 A1 = 1
An-An-1=4
An=4n-3
So a1000 = 4 × 1000-3 = 3997
Let 4n-3 = 4921
n=1231
So the number 1000 result is 3997
4921 is his 1231

In a column of numbers 1, 2, 3,. 1000, what is the frequency of the number 0? Write out the calculation process... Quick

Single digit: No
Double digit: 9 (10,20,... 90)
Three digit: ten digit: 90, one digit: 90
4 digits: 3 (1000)
A total of 192

In a column number 1,2,3,4 In 1000, the number of times the number "0" appears is ()
The answer I got was 172, but I didn't choose 172
A、182 B、189 C、192 D、194

I don't like to post answers. The answers are not easy to understand. Listen to my analysis
1. In the single digits 1-9, there is no 0
2. In the two digit 10-99, because the tens can't be zero, only the ones can be zero, it's obvious that when the ones are zero, there are only nine possibilities for the numbers on the tens. Therefore, there are only nine numbers containing 0 in the two digits, each containing one 0. Therefore, there are 9 * 1 = 9 times of zero in the two digits
3. In the three digit 100-999, we have two cases: including one 0, including two 0
a) If 0 contains 1 0, then it is either in the individual or in the ten. When 0 is in the individual, there are 1-9 possibilities for the number of hundreds and ones, then 9 * 9 = 81. Similarly, when 0 is in the ten, there are also 9 * 9 = 81. In this way, there are 81 + 81 = 162 three digits containing 1 0, and 162 * 1 = 162 times of occurrence of 0
b) If there are two zeros, then the one digit and ten digit are all zeros, and the hundred digit can only be 1-9, then there are nine such numbers, with a total number of zeros of 9 * 2 = 18
4. There's only one thousand in four digits. Obviously, there are three zeros
Let's add the above results up to 9 + 162 + 18 + 3 = 192
Choose C

The number of columns is 1,3,11,67629,2,3,6,9,17,27, - 7,0,1,2,

So the next number should be the 5th power of 6 + 5 = 7781, then the answer to the first question mark is 7781
2 + 3 + 6 = 11, 3 + 6 + 9 = 18, 6 + 9 + 17 = 32, 9 + 17 + 27 = 53, 17 + 27 + x = y, 11 + 7 * 1 = 18, 18 + 7 * 2 = 32, 32 + 7 * 3 = 53, 53 + 7 * 4 = y = 81, that is to say: 17 + 27 + x = y = 81, then x = 37
The answer to the second question mark is 37
The answer to the third question mark. Cough. To be honest, I can't do the third question. I'd better ask someone from the math bar to help me
（-2）^3+1,(-1)^3+1,0^3+1,1^3+1,2^3+1=x=9
So the third question mark is 9

There is a column of numbers: 2 / 3, 5 / 6, 10 / 11, 17 / 18, 26 / 27. The nth (n is a positive integer) is

Looking at molecules
2 = 1 square + 1, 5 = 2 square + 1, 10 equals 3 square + 1
The nth is the square of N + 1
The denominator is numerator + 1
So the nth is (n ^ 2 + 1) / (n ^ 2 + 2)

There are three numbers a, B and C. The average number of a and B is 15, the average number of B and C is 19, and the average number of a and C is 17?